This paper presents a methodology to analyse the thermal loads of non-residential buildings based on simplified weather data, which are available for 206 Brazilian locations. These data include monthly average of maximum and minimum temperatures, atmospheric pressure, cloud cover and relative humidity. For each month, two typical days are used to estimate the cooling and heating loads. The Transfer Function Method was used to run load calculations and the validation was evaluated according to ASHRAE Standard 140. The methodology showed good results for cases with low mass envelope but revealed limitation to represent thermal inertia influence on the annual cooling and heating loads. (C) 2004 Published by Elsevier B.V.